A blowout preventer (BOP) is a safety assembly which is provided at a desired location in a wellbore and is adapted to seal the throughbore of the assembly in an emergency situation. Conventional BOPs generally have a number of wellbore sealing members which can be deployed across the throughbore of the assembly in order to seal the wellbore. Such wellbore sealing members are typically provided in the form of gates or rams. There are usually a number of opposed gates or rams, typically provided in pairs on either side of the throughbore, and which are movable in a plane transverse or perpendicular to the throughbore. In the event of an emergency, the rams/gates are moved towards each other to cut any object in the wellbore and seal the wellbore.
In order to allow shearing of any object that may be located in the wellbore, the rams/gates are provided with cutting/shearing blades configured to cut through any wellbore equipment which may be located between the rams, such as a tubular or a wireline. Once the rams/gates have severed through the wellbore equipment, and are engaged with each other and/or with a respective seal seat, the wellbore is sealed.
International Patent Application Publication No. WO 92/13170 (Smith et al) discloses a shear ram blowout preventer apparatus having an upper ram block having an inset in a laterally inward surface thereof, to aid in positioning a borehole retrievable, for example, a multi-strand cable, for cutting relative to a notch of a blade member.
U.S. Pat. No. 4,986,360 (Laky et al) discloses a system for handling reeled tubing, the system including a pair of cutting blades having horizontally extending cutting edges, and semi-circular cut-outs adjacent the cutting edges to assist in maintaining a cut and crimped pipe in semi-circular form.
A problem in the prior art is the inability of the gates to effectively cut or shear the different types of objects that may be located in the wellbore in the event of an emergency.
It is an object of the present invention to eliminate or mitigate one or more of the disadvantages associated with the prior art.